Apparatus for making blueprints



Oct. 29, 1940. H; J BRUNK APPARATUS FOR MAKING BLUEPRINTS Original Filed March 14, 1935 Jfafoidcffigwu g, A 2J0, A

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PATENT OFFICE APPARATUS FOR MAKING BLUEPRINTS I Harold J. Brunk, Chicago, Ill., assignor to The C. F. Pease Company, a corporation of Dela- Original application March 14, 1935, Serial No. 11,141. Divided and this application February 16, 1938, Serial No. 190,855

4 Claims My invention relates to improvements in apparatus for making photographieprints, including blueprints, and is directed more particularly to the substantial elimination of so-called bleeding, which in the case of blueprints means the discoloration of the white areas by the blue coloring material. This application is a division of my application Serial No. 11,141, filed March 14, 1935, in which the method is claimed.

In developing ordinary blueprints, i. e., sheets of paper having sensitized coatings, which, when exposed to light and washed with water have a blue background with white lines on it, the blue in the background runs over the white line giving it a bluish cast and at the same time closing up on the line making it narrower than the opaque line on the original tracing, and in fact at full exposures, intended to bring out the deep Prussian blue color of the background, the line may be lost completely.

Also, when making blue line prints, i. e., similarly coated paper with blue lines on a white background, printed from negatives or tracings, the fully exposed chemical in the area outside of or between negatives runs down into the white background and stains it blue immediately, when water is applied to the surface of the paper. In addition, the blue lines themselves, at certain exposures, run down into the white background giving them a ragged appearance.

These difficulties are inherent in the usual method of making blueprints, due in part to the chemicals used and in part to the application of water to the span of blueprint paper while it is traveling through a continuous blueprint machine in a plane which is vertical or inclined, i. e., by causing the water to flow over the paper. Said difficulties and the chemical reactions which take place, as well as a method of overcoming the difliculties, are discussed fully in Patent 1,861,298, issued May 31, 1932, based on my application filed May 11, 1931. Said method involves the use of a special developer before applying any water to the print, and is successful even when the blueprinting machine is operated at a comparatively high rate of speed. Said patent states that the range of speed for average printing is from six inches to twelve feet per minute. The method of in making blueprints, except for an additional preliminary water treatment of a special character, and, furthermore, the equipment used may be very similar in general to standard continuous blueprint machines except for a few attachments and incidental alterations.

The object of the invention is to provide new and simple means for overcoming the difllculties heretofore inherent in the use of water in developing blueprints.

A contributory object is to provide means for applying water to the coated surface of the sheet to start the oxidation of the chemicals comprising the coating, but without permitting the water to flow along said surface to any substantial extent.

Another object is to provide means for applying water to the coated surface of the sheet, in two installments, the first of which is applied with little or no relative movement f the water with respect to the sheet, to avoid causing the chemicals to spread over said sheet; and the second of which is applied more vigorously to give' the sheet a thorough washing. 7

Another object is to provide mechanism for causing an exposed sheet of blueprint paper to travel through a water bath upside down, i. e., with the coated surface below the sheet, whereby the water starts the oxidation of the chemicals, and, more particularly, the surplus chemicals which are washed from the sheet fall away from the same and descend in the tank instead of being carried along and causing a mingling of the exposed and unexposed portions of said chemicals on the surface of said sheet.

In the accompanying drawing I have illustrated one embodiment of the invention in the form of an attachment to a well known type of a so-called continuous blueprinting machine, which will serve to illustrate its advantages.

Fig. 1 is a side elevation of part of said machine;

Fig. 2 is a top plan view of the tank and certain accessories, and i Fig. 3 shows a portion of Fig. 1 in vertical section on an enlarged scale.

Describing the operation of the machine very briefly, the span of coated paper is fed rearwardly and then upwardly past a source of light where the printing is accomplished. Afterward the paper is passed horizontally through a bath of still water, the paper being upside down, thus removing surplus chemical and initiating the oxidation, whichsteps prevent subsequent running or bleeding of the color when the paper passes through the usual water wash. This washing is followed by the potash bath, after which the print is washed and dried. The coating generally used, is well known, be ing applied as a solution containing mixtures of potassium ferricyanide and organic salts of iron such as ferric ammonium oxalate. During the period of exposure to such lightthe potassium ferricyanide is partly reduced to potassium ferrocyanide whilethe ferric ammonium oxalate is reduced to ferrous ammonium oxalate.

Referring now to the machine more in detail, it comprises a suitable frame consisting of parallel side members members, and supporting the various rollers and other parts hereinafter described. The blueprint paper, to be used with the machine is supplied in the form of a roll I I, mounted near the front of the machine and is drawn from the roller as a long span I2 which travels past a curved sheet of glass l3 with the coated or sensitized side of the paper on the side toward'the glass but with the tracings or negatives between it and said glass and facing a suitable source of illumination, which, in this case, is preferably a row of arc lamps. This printing section of the machine is of standard construction and need not be described in detail. After printing, the paper passes over an idle roll I4, thence downwardly past another idle roll l5 and under a tension roll IS, the latter being guided to move up and down in suitable ways and partially counterbalanced in any well known manner.

From the tension roller IS, the span of paper passes over the idle rollers I1 and I8 and thence downwardly and under the idle rollers I9 and 20 which are spaced apart horizontally so that the paper travels from one to the other in a substantially horizontal span with the coated side facing downwardly. The lower part of said rollers and the horizontal span of paper are immersed in water in a suitable receptacle or tank 2|, said horizontal span, as shown in Fig. 1, being not very far below the surface of the water, and hence the paper, as it travels downwardly and around the roller l3, travels only a short distance before assuming a horizontal position. The supply of water is introduced in such a way as to avoid violent agitation thereof. For example, it may be delivered through a pipe 22 having orifices through which it may be sprayed downwardly into a special compartment formed by a partition 23, and after filling the tank to the level of the overflow pipe 24, the supply is maintained continuously but without causing any substantial current within the tank. Thus the horizontal span of paper travels, preferably at a slow rate, through a bath of comparatively still water so that there is relatively little movement of the water with respect to the paper. Also, it will be seen that the coated side of the paper does not come in contact with the rollers I9 and 20 nor with anything other than the water, after the paper has been moistened. In the l0 connected by suitable crossoxidation and also loosens and removes the superfluous chemicals, i. e., any chemicals not reduced or partially reduced, as they are soluble in water, whereas the chemicals reduced by exposure to light are insoluble. The unexposed chemicals which fall away from the paper, do so without traveling along its surface, as said chem icals are somewhat heavier than the water. This method of washing is effective in very materially reducing the bleeding or migration of the color which would take place otherwise during the subsequent washing. Also it preserves the tone of the whites or blue line prints. In other words, a clean, fast color is produced and the condition of the print is such that it can later be washed more thoroughly and completely, as hereinafter described, without any bleeding of the blue areas into the white areas.

As the horizontal span of paper passes from roller l9 to roller 20 and becomes saturated with water, it expands and would wrinkle as it passes around the roller 20 but for the provision of bent tubes or bulgers 25, well known in the art, which are mounted so as to cause the paper to pass 'over them in a span which is not quite flat but curved in'transverse section. These rods are mounted at the ends in suitable journals 26 and may be adjusted by means of cranks 21 and handles 28. Additional bent tubes are mounted on the inclinedsupport 23. The stretching of the paper lengthwise is automatically compensated for by the tension rollers l6, previously described.

After leaving the still water bath, the span of paper i 2 passes along an inclined path to the water wash 30, which may be of any suitable or approved type either in the form of a spray wash or rollers. The roller type is shown in the drawing as comprising a roller3l over which the span of paper passes, thence under a roller 32 and up over an elevated roller 33. Water is sprayed onto the roller 32 from a suitable pipe 34. Thus the paper is thoroughly washed to remove any trace of soluble chemical, and at this point there is no bleeding of the color, because of the initial application of moisture, just described. This main water wash also furthers the oxidation process. Another pipe 35 provides a second spray which is discharged directly onto the paper as it passes over the roller 33.

From the water wash the paper passes over an idle roller 36, thence downwardly past another roller 31 against which a spray of water may be directed from a pipe 38 for the purpose of moistening the back of the paper so that the same will be uniformly moistened throughout. This span being nearly vertical, the water from the pipe 38 continues to flow over it in a thin film to prevent wrinkling. The span of paper then passes under a roller, not shown, and thence to the point where it is treated with potash, i. e. bichromate of potash, or other well known oxidizing agent to complete the oxidation begun by the water and to intensify the blue tone. The paper passes next a final water wash and then through the drier and is stored temporarily on a roll from which it may be cut as desired.

The process described, while it will not stop all bleeding under all speed conditions, is, nevertheless, very satisfactory in materially reducing the bleeding, and in the case of the slower printing papers which are necessarily fed through the machine at comparatively low rates of speed, i. e., at rates below and not to exceed possibly four feet a minute, the bleeding is substantially eliminated. As the carrying out of the method requires nothing but the use of water and equipment similar to or almost identical in certain of its detailed parts with equipment ordinarily used as part of continuous blueprint machines, the method constitutes a considerable advance not only from the standpoint of results attained but from the standpoint of economy.

I claim:

1. A blueprint machine comprising a tank for water, a pair of spaced-apart rollers adjacent said tank and mounted to rotate with their lower surfaces below the water level of said tank, means for moving a continuous band of paper coated with light-sensitive material past and in contact with the under sides of said spaced-apart rollers with the uncoated side in contact therewith and the coated side facing downwardly, whereby said band travels beneath the surface of the water from one roll to the otherto moisten said band and whereby such excess chemicals as are removed from said band descend in said water without further contact with said band, and means beyond. said tank; to which said band travels, for washing said band to remove further chemicals therefrom.

2. A blueprint machine comprising means for conveying a continuous band of paper coated with light-sensitive material past a pair of spaced apart rollers with the uncoated side in contact therewith, a tank containing a water bath in which said band travels beneath the surface from one roll to the other to moisten said band, whereby such excess chemicals as are removed from said band descend in said water without further contact with said band, means beyond said tank, to which said band travels, for washing said band to remove further chemicals therefrom, and curved transverse members in said tank engaging said band between said rollers to smooth out the wrinkles in said band caused by expansion thereof.

3. An attachment for blueprint machines having a washing station comprising a plurality of rollers and a tank of water, certain of said r0llers being positioned to cause the blue print traveling in contact with them to pass through said tank of water upside down, and curved transverse members in said tank to engage said blueprint between said rollers to smooth out the wrinkles in said print caused by the expansion thereofwhen wet.

4. A blueprint machine having a pair of rollers spaced apart in parallel relation, a container for water in which said rollers are partially submerged, and transverse members curving downwardly in the water, means for drawing a continuous blueprint down and under one of said rollers, then substantially horizontally in a span submerged only slightly below the surface of said water and in contact with said curved members with its coated side facing downwardly and then around the other roller and upwardly out of said container, whereby development of the coated surface takes place without migration of the chemicals from one part of the coated surface to another and whereby said print passes under said other roller without wrinkling.

, HAROLD J. BRUNK. 

